1. Field of the Invention
The present invention relates to an IC card having a writable memory and more particularly to an IC card for writing a program in this memory by keeping security and a method thereof.
2. Description of the Prior Art
An IC card is excellent in security and finds wide applications. Generally, an IC card has a built-in memory for writing and storing a program as well as various information which can be erased electrically and is used to write various information after a user owns it. For example, the invention disclosed in Japanese Laid-Open Patent Application 6-309558 stores customer information in an IC card and provides quick services. In Japanese Laid-Open Patent Application 6-309384, a use that inspection results and dosing data of a patient in a medical institution are stored in an IC card is described. Furthermore, recently, study has been given to use of an IC card in an electronic money system and an IC card is used to write money information.
As mentioned above, the use method of writing information in an IC card is generally carried out. To keep security, the use method of changing and adding to an internal program stored already and writing a new program is limited.
To improve or change the function of an IC card, there is a case that changing of a program is necessary. Furthermore, to keep security, a case that changing of the cryption method is necessary also may be caused. However, to make it possible to modify an already stored program leads to information opening to public of the microprocessor chip of the IC card and the program thereof and it is not suitable for the use of this IC card for which high security is evaluated.
Therefore, an object of the present invention is to provide an IC card for changing or adding to an internal program with the high security of an IC card kept and writing a new program and a method thereof.
To accomplish this object, the present invention is a program writable IC card comprising a microprocessor and a memory for storing a program write control program having at least one of the decryption function and the function for converting a program code and a program for the aforementioned microprocessor, wherein when the program for the microprocessor is given from the outside, the IC card performs at least one of the decryption process and the process of converting a program code according to the program write control program and stores the program in the memory.
More concretely, according to the present invention which is a program writable IC card comprising a microprocessor and a memory storing a program for the microprocessor, one characteristic is a constitution that the IC card includes a write control program having the decryption function and/or the program code conversion function in a program built in the IC card and a memory for program writing and the other characteristic is a constitution that the IC card includes a write control microprocessor for executing the write control program having the decryption function and/or the program code conversion function in addition to the microprocessor for IC card, a means for switching the two microprocessors, and a memory for program writing.
Another characteristic of the present invention is a constitution that the IC card having a microprocessor whose technical information such as a specification is not opened to public includes a microprocessor whose technical information such as a catalog and a specification is opened to public, a memory for program writing for storing a program for the microprocessor, and a means for switching the two microprocessors.
These constitutions make it possible to change or add to an internal program by keeping the security necessary for the IC card and to write a new program.